Variable condenser



Jan. 24, 1928.

J. G. RECORD VARIABLE CONDENSER 2 Sheets-Sheet 1 Filed Dec. l 1926 Mam 7'02, JbMEs 61 856020 ATTORNEY Jan. 24, 1928. 1,657,135

- J. G. RECORD VARIABLE CONDENSER Filed Dec. 11. 1926 2 Sheets-Sheet 2 ME Toe, .IqMES 6; 250020 4 T TOE/V5 Y Patented Jan. 24, 1928.

UNITED STATES JAMES G. RECORD, OF GARDENA, CALIFORNIA.

VARIABLE CONDENSER.

Application filed December 11, 1926. Serial No. 154,180.

This invention relates to electrical condensers, and especially to variable condensers such as are used in radio apparatus for varying the electrical characteristics of a circuit, or for tuning a circuit. The application of variable condensers to this field is well-known, and needs no further elucidation.

An ordinary type of variable condenser includes a pair of sets of parallel plates, each set forming an electrode, and interleaving with each-other to a variable extent. In such condensers, the plates are relatively rotatable, and the extent of angular motion necessary to change from minimum to maximum capacity is approximately 180. It is evident therefore that such an arrangement requires a comparatively large rate of variation. It is one of the objects of my invention to make it possible to produce a gradual variation for a complete revolution of relative motion.

I am able to produce this result by providing one of the relatively movable plate structures with a pair of sections which are.

brought alternately into action as. the condenser is operated. This action is accomplished by switching means operated as the condenser is varied. It is accordingly another object of my invention to make it possible to render only a portion of the relative ly movable structures active, and especially so that the change from one'portion to another is accomplished without any abrupt variation in the capacity.

It is another object of my'invention to improve in general, variable condensers of the relatively movable plate type.

My'invention possesses many other advantages, and has other objects which may be made more easily apparent from a consid eration of several embodiments of my invention. For this purpose I have shown a few. forms in the drawings accompanying and forming part of the present s ecification. I. shall now proceed to descri e these forms in detail, which illustrate the general principles of my invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of my invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a sectional view of one form of condenser embodying my invention taken along plane 11 of Fig. 2;

Fig. 2 is a sectional view, taken along plane 2-2 of Fig. 1;

Fig. 3 is a sectional view, taken along plane 33 of Fig. 1;

Fig. 4 is another sectional view, taken along plane 44 of Fig. 1;

Figs. 5, 6 and 7 are diagrammatic views showing various forms of electrode plates that can be used in my condenser;

Fig. 8 is a fragmentary sectional view of a modified form of my condenser;

Fig. 9 is an end view thereof;

Fig. 10 is a detail section taken along plane 1010 of Fig. 3;

Fig. 11 is a detail perspective view of a porition of thecondenser shown in Fig. 1; an

Fig. 12 is a detail sectional View taken along plane 1212 of Fig. 9.

I show my condenser as mounted on a panel 11 (Fig. 1) which has a clearance hole 12 to permit passage of the condenser op erating shaft 13 from the rear to the front of the panel. All of the operating parts are back of the panel, the extending portion of shaft 13 merely serving to accommodate some form of setting indicator, such a dial 14 and its digitally movable knob 15.

In order to hold the structure to panel 11, use is made of a series of spacing rods 16 (four in this instance) that are shown as hexagonal (see Fig. 2) and as provided with a through tapped aperture 17. Flat head screws 18 pass through panel 11 and engage these spacers. A metallic supporting spider 19 is fastened to these spacer supports as by screws 20 passing through the spider 19.

This spider has in this instance, four radial arms, at the extremity of each of which there is an arcuate bifurcation 22. The adjacent ends of these bifurcations are joined by short strips 23. Of'course other forms of metallic supports could be used, but the present one combines simplicity and strength.

The bifurcations 22 each serve to support a corner piece 21 of insulation material, such as bakelite, rivets 24 being shown for fastening the parts together. The fastening screws 20 pass through these pieces 21 also, as clearly shown in F1g. 1. a

From corner pieces 21, supporting elements are provided for holding stator plates and 26. The form of these plates shown most clearly in Fig. 4, but obviously this can be varied so long as certain requirements are met, as will be explained hereinafter. The arrangement is such that only one of the two sets of plates is active at a time, whereby the rotor plates, moving through one-half revolution, coact say first with plates 25, and during the second halfrevolution, with plates 26. By appropriate formation of the plates, the variation in ca pacity for the entire revolution can be made to conform with any law, such as straight line frequency. For the present, however,

- I shall proceed to explain the manner in which the stator plates are supported.

A metallic nut 27 is held to each corner piece 21 by a screw 28. Threaded into the nut is a. stud 29 upon which are alternately placed the spacer bushings 30 and the plates 25 or 26. Each plate is thus held on two of the studs'29 as'shown in Fig. 4. The bushings and plates are held in place by threaded nuts 31 engaging'studs 29. These in turn serve to support the back plate 32 of insulation, such as bakelite, by the aid of screws33.

The rotor plates 34 interleave with th stator plates 25 and 26 and are supported on the shaft 13. This shaft has a portion 35 upon which are disposed alternately the spacers 36 and the rotor plates 34. in order to provide axial adjustment of all of the rotor plates 34 on shaft 13, a nut 37 is threaded on the shaft adjacent the large end thereof, serving as an abutment for the first rotor plate. A similar nut 38 is provided at the other end for clamping the plates on the shaft. A bearing bushing 39 is threaded in spider 19 to provide an adjustable abutment against which nut 37 operates: and by adjusting this bushing, the axial position of shaft 13 can be varied to bring plates 34 into proper position with respect to the stator plates. At the other end of shaft 13, there is a bearing bushing 40 in plate 32 in which the shaft. is accommodated. A nut 41 and its check nut serve to provide an abutment for preventing the shaft 13 from moving axially once it is adjusted. A metal strip 42 is clamped between the nut 41 and the support 32, which can serve the dual purpose of a connection to the rotor as well as a friction producing means for retaining the condenser in any set position. The latter function is obtained by splitting the end of the strip 42 where thenut engages it, and springing the split parts apart, thus causing it to act as the usual spring lock washer.

The shape of plates 34 is shown in dotted outline in Fig.4. In this figure it is also seen that plates 26 are slotted, as at 43. This is esse t al t permit assembly, th

plates 25 being first fastened to the pider arrangement 19, thenthe shaft 13 and its assembled rotor plates are slipped in below these plates. To accomplish this result, the

rotor plates 34 are in a position 180 away from that of Fig. 4; that is, in the position of Fig. 2. Under such circumstances, since there is no overlapping of plates 25 and 34, the axial movement of shaft 13 to position it in the structure is permitted. After the rotor is thus put in place, the stator plates 26 are assembled on studs 29, the slot 43 permitting them to straddle shaft 13 which is already in place.

It is now possible to detail the mode of coaction of the sets of relatively movable plates. Referring to Fig. 2, it is seen that the rotor plates 34 are directly superposed over the stator plates 26, these two sets of Jlates havin somewhat similar contours.

For minimum capacity setting, stator plates 26 are inactive, and plates 25 only, are active, and the relation of the plates is as indicated in Fig. 2, there being no interleaving at all between the active plates 25 and 34. Upon rotation of plates 34 in a counterclockwise direction, more and more interleaving is effected between these sets of plates. increasing the capacity. This continues for a hal trevolution, when maximum interleaving between these plates is secured. This condition is shown in Fig. 4. The shape of plates 25 is such that substantially a straight line frequency variation is secured up to this point. It is also apparent from Fig. 4 that plates 26 interleave with plates 34 to a minimum extent. Further rotation of shaft 13 would increase this interleaving.

From this point on, and for the second half revolution, the plates 25 are inactive, and plates 26 are active. This change in the active plates can be accomplished by the aid of .appropriateswitching devices, operated by operation of shaft 13. It is seen that continued rotation will gradually increase the interleaving until rotor plates 34 are substantially covered by stator plates 26. This corresponds to maximum capacity setting, and is represented by Fig. 2, with the understanding that plates 25 are inactive, and plates 26 active. Continued movement from this position would cause 'a corresponding change in the active plates, the plates 26 becoming inactive and plates 25 active. Thus the cycle just outlined would be repeated during the next revolution.

It is especially to be noted that when the change in activity is accomplished after a half-revolution, it is desirable that such a change will not cause any sudden or abrupt variation in capacity. This can readily be accomplished by so forming the plates that means that. the overlapping areas of plates and 34 are the same as the overlapping areas of plates 26 and'34. It is seen that this condition is fulfilled in Fig. 4.

Of course, this latter condition must be fullfilled for smooth operation through the switching point even for different laws of capacity variation. Thus in the diagrams of Figs. 5, 6 and 7 I show the settings at the switch-over point for plates having different contours. In Fig. 5 the stator plates 44 and 45 are alternatively active, the switching being accomplished at the instant shown. Rotor plates 46 interleave with both stator sets by an equal amount. In Fig. 6 the rotor plates 47 and the lower stator plates 48 are of slightly different form from that of Fig. 5, but nevertheless the overlapped areas are balanced as before.- In Fig. 7 a still further change in form is indicated. In these vari ant forms the capacity variations differ for the same angular movement of the iotor, but otherwise the theory of operation is the same in all.

Before proceeding with the description of the switching means, it is advisable to discuss some of the advantages arising from this mode of operation. The condenser structure is compact, for with the same overall sizes of plates, a greater capacity variation can obviously be effected. For example if the old style condenser with but a single stator'be used for straight line frequency variation, the maximum capacity would be less than half as great as in my improved condenser. There is a corresponding advantage in the other cases of straight line wave length variation'and of straight line capacity variation, there being about a 75% advantage in the first case, and about a 30% advantage in the latter.

I shall now describe one form of switching apparatus whereby the change from one set of stator plates to the other is effected, although of course I am not limited to any specific form. The insulation plate 32 has embedded therein at one side thereof, a plurality of circular conducting segments 49, 50, 51 and 52. 'These are all concentric and arranged in pairs as indicated most clearly in Fig. 3. The opposite segments 49 and 51 are connected by a wire 53, and the other segments are also connected by wire 54. Segments 49 and 50 have spaced adjacent edges, and segments 51 and 52 are similarly spaced. A pair of spring blades 55 and 56 are arranged to coact with the segments 49, 50 and 51, 52 respectively, these blades being just wide enough so as not to connect to the segments 49, 50 or 51, 52 simultaneously. These blades are embedded in a rotatable insulation support 57, preferably of bakelite, whereby these blades can be embedded during molding.

The support 57 is pivotally mounted on the plate 32 as by the aid of a headed rod 58; the support has a bushing 59 for accommodating this rod. The rod is threaded at its end, and projects through a bushing 60 in plate 32. Nut 61 serves to position this rod with respect to plate 32. A lock washer 62 can be used back of plate 32 to. maintain the nuts tight; and if desired, the end of rod 58 can be spread as'by saw cut 63 to lock it against removal. In order to permit connections to be made to the blades 55 and 56, tabs 64 and 65 can be provided in support 57.. molded therein and integral with blades 55 and Segments 49 and 51 are in electrical connection with one set of stator plates, such as 25, as by the aid of a connection 67. Similarly, segments 50 and 52 are connected to the other set of plates 26 as by connection 69. One of the blades, such as 55 is connected by pigtail and terminal 71 to the rotor shaft 13; and the other blade 56 is similarly connected to a stationary terminal 72 serving as one of the terminals of the condenser. The other terminal 73 is fastened to the bar 42 and serves as the rotor way between their respective cooperating segments. However, upon even a slight rotation'of support 57, the blades 55 and 56 become active. If blade 56 connects with segment 52, the plates 26 are active; if with segment 51, then plates 25 are active. The other blade 55 serves merely to ground the inactive set of plates as by connecting it to the shaft; but such grounding is not essential. and blade 55 with segments 49 and 50 could be omitted.

Assuming then that blade 56 is contacting with segment 51, and blade 55 with segment 50, the stator connections from terminal 72 include blade 56, segment 51, connections 53 and 67, to plates 25. The rotor connections from terminal 73 includes bar 42 and shaft- 13. Since blade 55 touches segment 50, the plates 26 are grounded, through connections 69 and 54, segment 50, blade 55, connection 70 and terminal 71. However, as soon as the position of Fig. 4 is passed, the bladesfare caused to reverse; blade. 56 passing onto segment 52 and blade 55 to segment 49. Under such circumstances, the. rotor connections proceed from terminal 72 to blade 56, reg ment- 52, connection 69, to plates 26; and plates 25 are inactive and grounded through connection 67, segment 49, blade 55, connection 70 and terminal 71.

The manner in which the support 57 is moved to accomplish these results at the proper time will now be described. The last rotor plate 34 carries a pair of pins 74 and 75, which engage the support 57 on opposite Sides of the axis thereof so as to rock &

it. The friction between blades 55, 56 and the segmentstkeep the blades in adjusted position; although stop pins 76 and 77 of insulation material could be used to limit the blade movement. The support 57 is provided with a pair of opposite notches 78 and-7 9 which pins 74 and 75 are adapted to engage as they are brought into position by movement of rotor shaft 13.

The pin 75 is so located with respect to rotor plates 34 that as it moves through the position of Fig. 4, it rotates the support 57 by engaging notch 79. The direction of rotation of this'support depends upon the di rcction of rotation of the rotor, and is such that if the rotor moves in a counterclockwise direction, as viewed in Fig. 3, the support 57 (moving in a counterclockwise direction) moves blade 56 onto segment 52, and the stator plates 26 are rendered active, due to cooperation between this blade and segment '52. This movement therefore corresponds to an increasing capacity. A reverse movement, for reducing the capacity through the half-Way point, will cause blade 56 to engage segment 51, thus'making plates active.

Considering Fig. 2, it is evident that the 'plates in the position shown therein can correspond either to a minimum or to a maximum setting, depending upon which set of plates 25 or 26 is active. Therefore the switching arrangement must be such that at the full, revolution point of Fig. 2, the active plates are again altered, so as to return the condenser ,to a minimum capacity setting as soon as a second revolution is started. Pin 74 performs this function.

Continued counterclockwise rotation of the rotor will in time cause blade 56 to move clockwise, due to engagement of pin 74 in notch 78. This happens at the point of a -'fullrevolution, since pin 74 is 180 away from pin 75." This movement of the blade 56 causes it to engage segment 51, making plates 25 active, and whiohst-ay active until pin 75 again operates the blades in a reverse direction.

The advantages of the switching arrange ment just disclosed are of considerable value. There are no constantly rubbing contacts as the condenser is varied, the switching being accomplished once and for .all at the change-over points. The parts are ing 81 in support 82. This bushing is held in place by lock nut 85; and a, spring washer 86' is used to provide friction for retaining the rotor in its setting. It also has an extension 87 (Fig. 9) for providing a rotor terminal. In Fig. 9, the support 82 is omitted for the sake of clearness.

Near the inner surface of the support 82 there is another terminal connection 88 which provides a stator terminal. It has a collar portion that surrounds the insulation bushing 89, thus being lnsulated from rotor shaft 80. The bushing 89 however, is carried by the shaft, and serves to support a spring structure 84 comprising three fingers. This structure is in sliding contact with the connection 88, as clearly indicated in Fig.8. Theoutside fingers support a wiper 90 of insulation material, which rides over the end plates 25 and 26. The middle finger 92 however, forms the switch that cooperates with the stator plates to render them active. The insulation wiper 90 has a slot 91 through which middle finger 92 can act. A cross piece 93 of insulation is carried by the finger that is wide enough to bridge the space between the plates 25 and 26 and thereby toprevent the spring finger from entering too far between the sets of plates.

While one set of plates is rendered active,

the other is always grounded. This is ac- 1 complished by a spring structure 83 similar to structure 84 but grounded on shaft 80, as by the aid of the metallic sleeve 93 (Fig. 8) on which structure 83 is mounted. Since structure 83 is diametrically opposite to structure 84, it is seen that the inactive stator plates are grounded. thereby.

I claim:

1. A variable condenser having relatively movable electrodes, one of said electrodes being divided into two portions of unequal areas, and means whereby either of said divided portions is rendered active while the other is rendered inactive.

2. A variable condenser having relatively movable electr0des,zone of said electrodes being divided into two parts, said parts of unequal areas being angularly spaced from each other, and switching means for causing either of said parts to be activc and the other to be inactive.

3. The combination as set forth in claim 2.

with the limitation that the switching means is operated by the relative movement of the electrodes. 4. In a. variable condenser, a pair of relatively rotatable electrode structures, one of said structures being composed of two electric'ally distinct parts of unequal areas and arranged to form distinct angular portions around the axis of rotation, and means for causing either of said parts to be active and the other to be inactive.

5. The combination as set forth in claim 4, in which the means for rendering either Hill CJI

. arranged to form distinct angular portions around the axis of rotation, theother elec trode structure being arranged to overlap said parts to a variable extent as the rotation is eflected, and switching means operated by the relative rotation for rendering either of said parts active.

7. In a variable condenser, a pair of relatively rotatable electrode structures, one of said structures being composed oftwo electrically distinct parts and arranged to form distinct angular portions around the axis of rotation, the other electrode structure being arranged to overlap said parts to a variable extent as the rotation is effected, and switching means operated by the relative rotation for rendering either of said parts active, comprising means for shifting from one part to the other when the overlapping of both parts by the other electrode produces the same capacity between either of said parts and said other electrode.

8. In a variable condenser, a pair of relatively rotatable electrode structures, one of said structures being composed of two electrically distinct parts and arranged to form distinct angular portions around the axis of rotation, the coaction upon relative movement between one of the parts and the other electrode structure being such as to cause a variation from minimum capacityto an intermediate capacity value, and the coaction between the other of said parts and the other electrode being such as to cause a variation between the same intermediate value of capacity to a maximum value.

9. In a variable condenser, a pair of relatively rotatable electrode structures, one of said structures being composed of two electrically distinct parts and arranged to form distinct angular portions around the axis of rotation, the coaction upon relative movement between one of the parts and the other electrode structure being such as to cause a variation from minimum capacity to an intermediate capacity value, and the coaction between the other of said parts and the other electrode being such as to cause a variation between the same intermediate value of capacity to a maximum value, and means whereby the relative rotation causes a change in activity. from one part to another as said intermediate value is passed.

10. In a variable condenser, a pair of relatively rotatable electrode structures, one of said structures being composed of two electrically distinct parts and arranged to form distinct angular portions around the axis of rotation, the coaction upon relative movement between one of the parts and the other electrode structure being such as to cause a variation from minimum capacity to an intermediate capacity value, and the coaction between the other of said parts and the other electrode being such as to cause a variation between the same lntermediate value of capacity to a maximum value, and means whereby the relative movement of the struc-' tures beyond the maximum capacity value causes a reverse change in activity.

11. A variable condenser having relatively movable electrodes, one of said electrodes being divided, means whereby either of said divided portions is rendered active while the other is rendered inactive, and means whereby the inactive portion is electrically connected to the other electrode.

12. Avariable condenser having relatively movable electrodes, one of said electrodes being divided into two parts, said parts being angularly spaced from each other, and switching means for causing either of said parts to be active and the other to be inactive, and for connecting the inactive part to the other electrode.

relatively movable electrode structures, one

of said structures being divided, the divided parts having unequal effective areas and means for alternately connecting said divided parts to the other electrode.

15. In a variable condenser, a, stationary electrode structure, a rotatable electrode structure arranged to overlap the stationary structure, said stationary structure having two electrically distinct portions each occupying substantially 180 around the axis of rotation, the rotatable structure at one said portions so that the capacity between each is the same, and a switch operated by the passage of the rotary structure through this point for causing a/change from activity of one of said portions to the other.

16. The combination asse't forth in claim 15, in which the changing means .comprises a switch blade, a pair of segments cooperatpoint of its rotation overlapping each of ing with the switch blade and connected respectively with the two portions, and a prbjection carried by the rotary electrode structure for actuating said switch.

17. In a variable condenser, a' stationary electrode structure, a movable electrode structure, said stationary structure having a supporting plate of insulation material, and

a switch supported thereon and operated by pair of segments, a blade cooperating with the movable structure. 1 the segments, and amovable insulation sup- 10 18. In a variable condenser, a stationary port for the blade arranged in the path of electrode structure, a movable electrode travel of apart of the movable electrode 5 structure, said stationary structure having structure.

a supporting plate of insulation material, In testimony whereof I have hereunto set and a switch supported thereon and oper my hand. ated by the movable structure, comprising a JAMES G. RECORD. 

